BuiltWith - Find out the technology behind websites
Publisheet - Publish your Excel sheets to the web as dynamic web applications with formula support.
Wappalyzer - Wappalyzer is a technology profilers and leads data provider. Create lists of websites and contacts that use certain technologies.
SpreadsheetWEB - SpreadsheetWEB is a no-code platform that helps businesses translate their collective Microsoft Excel expertise into robust web applications with limited or no reliance on IT resources.
What CMS - WhatCMS.org looks at a variety of factors within a webpage to determine what CMS a website is using.
Appizy - Convert spreadsheet to web application